wrapture-instrumentation-mysql

Instrumentation for the MySQL client libraries, applied through wrapture.

wrapture attaches bindings to arbitrary Python call sites without modifying the code being observed, and its config layer can switch on packaged instrumentation for a third-party package by name. This is the MySQL package in that collection: one wrapture.Instrumentation class per client library, so tracing every query, connection and transaction your application sends to MySQL (or MariaDB, through the same drivers) is one config entry and no code.

Status: beta, ahead of 1.0.0. Developed against wrapture's beta series, with pre-releases published to PyPI, and until 1.0.0 is final a plain pip install wrapture-instrumentation-mysql picks up the latest pre-release automatically, so there is no need to pin a specific version.

Why a separate package

The core wrapture-instrumentation package deliberately covers only the standard library and third-party packages that can be exercised in-process, with no separate backend product or service needed to test against. A MySQL driver is exactly the kind of target the separate-package rule was drawn for: its tests need a real server, so this package's suite runs one in a docker container, and it carries the drivers as test dependencies (one of them built from source against a MySQL client library) and its own release cadence, so the core package's test matrix stays light. One package covers every client library for the one backend.

Installation

$ pip install wrapture-instrumentation-mysql

Installing it brings wrapture and nothing else. No driver is a dependency: each instrumentation is inert until its driver is present, and wrapture checks the installed version against the range the instrumentation supports at apply time.

Using it

An [[instrument]] entry in wrapture.toml names the target:

[[instrument]]
name = "pymysql"

[[sink]]
type = "printer"

and the runner applies it before the application starts, so the patch is in place before the driver is imported:

$ python -m wrapture -m myapp

The same config works through autowrapt injection (AUTOWRAPT_BOOTSTRAP=wrapture python myapp.py); through manual setup, a few lines in the application's own startup where wrapping the launch from outside is awkward; and, in a test, through wrapture.instrumentation("pymysql") scoping the instrumentation to a block. The ad-hoc tracing guide covers the config file itself.

To see what is installed, what it supports in the current environment, and what aspects and settings it takes:

$ python -m wrapture.tools instrumentation --verbose

Provided instrumentation

The entry point name is the config's name, and is the import name of the package the instrumentation patches (so mysqlclient's is MySQLdb); the linked per-target README is the full user documentation: what records, what the events carry, the aspects and the setting, and what is deliberately not traced.

What is not traced

By design, and where it goes:

• Fetching rows: a query event closes when its execute returns, so time spent iterating rows afterwards is the application's. An unbuffered cursor (SSCursor) therefore records the send and the wait for the first packet, not the streaming of the rows.

• The connection's context manager: in these drivers leaving a with connection: block closes the connection and performs no commit or rollback, so it is not a transaction boundary and records nothing. The explicit commit() and rollback() calls do.

• Mode changes and housekeeping (autocommit(), select_db(), ping(), set_character_set(), show_warnings()): not database operations in the sense the events record.

• Pool bookkeeping (aiomysql): taking a connection from a pool and returning it are not database operations; the connections the pool opens do record.

• LOAD DATA LOCAL INFILE records as a statement like any other; the file's contents never do.

Testing against a server

The test suite drives the real drivers against a real MySQL server. WRAPTURE_MYSQL_URL in the environment names one (mysql://user:password@host:port/database); without it the suite runs a throwaway mysql:8.4 container itself, which needs Docker Desktop or another docker daemon. With neither it fails rather than skips. The mysqlclient driver builds from source against a MySQL client library, so its suite runs inside a docker container that carries the toolchain (just test-docker), and a plain native run skips that one suite visibly rather than asking for a client library on the machine. TESTING.md covers the details, including how the suite copes with MySQL 8's caching_sha2_password authentication (the readiness probe's first connection warms the server's credential cache, after which every driver connects plainly; a real application on a cold cache over a plain socket needs the driver's own RSA or TLS option, which is the driver's concern, not the instrumentation's).

Adding a target

Each client library is its own subpackage and entry point here. The subpackage's __init__.py holds one wrapture.Instrumentation subclass and imports only wrapture (and the package's own common.py, which imports only wrapture too); everything that touches the driver lives in sibling modules imported inside the hook. The class is registered in pyproject.toml under [project.entry-points."wrapture.instrumentation"], and gets its own test suite under tests/<target>/ and a README.md linked from the table above. The instrumentation packages page of the wrapture documentation is the full contract; TESTING.md here covers the tests and the server they run against.

License

BSD 2-Clause. See LICENSE.